--- a/editor/libeditor/HTMLAnonymousNodeEditor.cpp
+++ b/editor/libeditor/HTMLAnonymousNodeEditor.cpp
@@ -234,17 +234,21 @@ HTMLEditor::CreateAnonymousElement(nsIAt
     }
   }
 
   ManualNACPtr newContent(newContentRaw.forget());
 
   // Must style the new element, otherwise the PostRecreateFramesFor call
   // below will do nothing.
   if (ServoStyleSet* styleSet = ps->StyleSet()->GetAsServo()) {
-    styleSet->StyleNewSubtree(newContent);
+    // Sometimes editor likes to append anonymous content to elements
+    // in display:none subtrees, so avoid styling in those cases.
+    if (styleSet->MayTraverseFrom(newContent)) {
+      styleSet->StyleNewSubtree(newContent);
+    }
   }
 
   ElementDeletionObserver* observer =
     new ElementDeletionObserver(newContent, parentContent);
   NS_ADDREF(observer); // NodeWillBeDestroyed releases.
   parentContent->AddMutationObserver(observer);
   newContent->AddMutationObserver(observer);